In active matrix type display apparatuses such as liquid crystal display apparatuses or organic electroluminescence (EL) display apparatuses, thin film transistors (TFTs) are widely used as switching elements or driving elements.
In recent years, techniques that use an oxide semiconductor for a channel layer of a thin film transistor have been studied. For example, PTL 1 discloses a technique for depositing an oxide semiconductor film by using a sputtering method.